1. Field of the Invention
The present invention relates to a method of doubling a vertical line speed for a high definition television (HDTV) camera for domestic use and a device thereof, and more particularly, to a method of doubling a vertical line speed by which the number of vertical scanning lines are doubled in order to obtain vertical line frequency for HDTV using a general-purpose 4-charge coupled device (CCD) and to a device thereof. The present invention is based on Korean Application No. 96-30878, which is incorporated herein by reference.
2. Description of the Related Arts
In general, digital broadcast for a wide television or an HDTV has an aspect ratio of 16:9, rather than 4:3 of a conventional NTSC broadcast. Accordingly, the digital broadcast cameras for a business or a general broadcasting system require various standards.
Currently, a single-layer CCD (LCCD) used for the camera is mainly for domestic use, and a triple-layer CCD (3CCD) is for business use or a broadcasting station. As the number of the CCD is increased, performance of the camera becomes better, but the apparatus becomes more costly. A quadruple-layer CCD (4CCD) camera having a structure more complicated than that of the 3CCD camera has better performance than that of the 3CCD camera. Also, the 4CCD camera can obtain the output of the camera, meeting the standards of the HDTV and resolution thereof. Here, the standards of the HDTV means the Japanese High-Vision standards having 1035 effective vertical lines of 1125 total vertical lines and 1920 effective horizontal pixels of 2200 total horizontal pixels, and the GA-HDTV standards proposed by Grand Alliance of U.S.A. having 1035 effective vertical lines of 1125 total vertical lines and 1258 effective horizontal pixels of 1440 total horizontal pixels, the ATV standards having 1080 effective vertical lines of 1125 total vertical lines and 1920 effective horizontal pixels of 2200 total horizontal lines, and the HD standards having 1024 effective vertical lines of 1125 total vertical lines and 1008 effective horizontal lines of 1200 total horizontal lines. The HDTV camera employing 4CCD for domestic use is inexpensive and interchangeable for use in the existing NTSC and wide TV. For the domestic use 4CCD camera, Hi-Vision standards of 16 to 9 in which the number of total pixels are 808H.times.518V, wide-TV standards of 16 to 9 in which the number of total pixels are 754H.times.485V, and SD NTSC standards of 4 to 3 in which the number of total pixels are 566H.times.485V can be used.
FIG. 1 is a block diagram showing a schematic structure of a camera system employing a conventional 4CCD. Each signal output from G1 CCD 102, G2 CCD 104, R CCD 106, and B CCD 108 is processed as an analog signal in each pre-amplifier (PA) 112, 114, 116, and 118, respectively, and then input t o an A/D converter 120.
Four channels converted to digital data in the A/D converter 120 (i.e., the outputs of G1 (Green 1), G2 (Green 2), R (Red) and B (Blue)) are supplied to a G vertical line doubler (VLD) 130 and an R/B VLD 140. Here, the green (G) channel, whose signals are approximately 70% of all signals and have high light-receiving sensitivity, are comprised of two channels. That is, the G channel can be constituted by G1 and G2 channels using a line memory (not shown) of 2H delay, in which H is a horizontal sync period, respectively.
A speed of a R(Red)/B(Blue) channel is doubled through two lines each using the line memory of 2H. Accordingly, when a line frequency of 16.875 KHz is input to the G and the R/B channels, a line frequency of 33.75 KHz, which is twice the input line frequency, is output. The line frequency input to the line speed doublers of G and R/B channels is 16.875 KHz, and the line frequency output therefrom is 33.75 KHz. Here, the line frequency of 33.75 KHz is based on a formula 1125.times.30, where 1125 indicates the number of lines per frame and 30 indicates the number of frames per second in the case of the HDTV. Accordingly, the line frequency shown in FIG. 1 can be changed by frame rate per second or line number per frame, and the input line frequency is half the output line frequency.
A general CCD usually supplies data of approximately 500 lines per frame. However, since the HDTV broadcasting requires data of approximately 1000 lines per frame, the vertical line doubler is required for HDTV employing the conventional CCD.
In the case of the G-channel output from the G VLD 130, vertical detail is processed in a detail digital signal processor (DSP) 150 having a memory (not shown) of 2H, and data of the detail-processed G channel is input to a color matrix 160.
The color-difference (G-Y) signal output from the color matrix 160 and the G channel signal output from the 2H detail DSP 150 form a luminance (Y) signal in a subtracter 162, and the Y signal and color-difference signals Pb and Pr output from the color matrix 160 are converted to analog signals via a D/A converter 170.
As shown in FIG. 1, in the case of a conventional G channel, between VLD devices 130, 140 and the color matrix 160, detail horizontal and vertical signals are processed using 2H memory (not shown). Here, the G channel is delayed by 1H, and the R/B channel does not perform detail-processing, to thereby generate a signal delay difference of 1H between the G-channel and the R/B channel.